Thermocouple tube



Get. 24, 1939. 1E. Bueu.

' THERMocouPLE TUBE Filed oct. 12, 1937 J INVENTOR a/H/v E; JEL L ATTORNEY .S

Patented @eta 24, 1939 UNITED STATES PATENT o-FFICE THERMOCOUPLE TUBE John E. Buell, Birmingham, Ala.

Application October 12. 1937, Serial No. 168,680

2 Claims.I (Cl. 136-4) This invention relates to improved means for supporting thermo-couples in such a way as to exclude air from the tube normally used to surround the thermo-couple. The thermo-couple and its protective tube are of conventional form and the invention is particularly directed to means combined therewith for excluding air from the conventional protective tube. 'Ihe novel means includes an extension pipe formed of common relatively inexpensive metal carrying a stopper on its end remote from the thermocouple, which is adapted to be compressed so as to adequately exclude air, which would tend to oxidize the active elements of the thermo-couple. It is important to use an extension tube of considerable length because the compressible or reslient materials of which the Stoppers are made would `normally be melted or destroyed by the prevailing temperatures maintained in the immediate zone of the thermo-couple.

The above and more detailed features of the invention will be readily apparent from the following detailed disclosure when read in connection with the accompanying drawing.

In the drawing- Fig. 1 is a small scale view ofa furnace equipped with a thermo-couple and the-extension and sealing means of the present invention; Fig. 2 is an enlarged longitudinal section through a thermo-couple equipped with the extension pipe and air-excluding tube and related parts embodying the present invention; Fig. 3 is a horizontal section on line 3 3 of Fig. 2.

Referring in detail to the drawing, IIJ is a conventional type of thermo-couple including elements I I and I2 of dissimilar metals, these being covered with suitable porcelain insulators I3. The extreme end of the thermo-couple extends into a porcelain cup I4 of conventional form, which rests on the closed end I5 of a tube I 6, which is formed of a metal, such as chrome iron characterized by a high resistance to the corrosive action of furnace gases.

As ordinarily constructed heretofore insofar as I am aware, there has been no provision of means to prevent the entrance of air to the interior of the protective tube I6. 'This has resulted in the early destruction of the thermocouple due to the oxidizing action of the air on the highly heated metallic elements of such thermo-couple. The present invention aims to lengthen the life of the thermo-couple and one feature which contributes to this lengthened life is the means to be presently described for excluding air from the tube I6.

In accordance with the present invention, I secure a coupling I1 to the upper end of the tube I6, this coupling being carried by an extension pipe I8 formed of common and relatively inexpensive metal, such as steel, ordinary steel tub- 5 ing or pipe being suitable for the purpose. It is desirable that the pipe I8 be of considerable length, so as to position an air excluding stopper I9 a considerable distance from the heated zone 2U of the furnace 2l, in which the thermo-couple may be installed. The stopper I9 will preferably be of yieldable material such as rubber or the like, so that it can be forcibly compressed into engagement with the inner surfaces of the' pipe I8 and thus form an approximately air-tight or 15 hermetic seal. Rubber is a suitable material for the stopper and when rubber or like material is used it is important that the pipe I8 be of such length that the stopper will be located far enough away from the furnace to prevent its being melted. Engaging the top surface of the stopper, there is a fibre disc 22, which is adapted to coact with the stopper and with a cap 23, which has a screw threaded engagement with the threaded endv24 of the pipe.

As thus arranged, it is clear that by screwing 25 down the cap the fibre disc will cause the material of the stopper to yield or be compressed so as to bring about the hermetic or air excluding seal in the end of the pipe. The rubber stopper 30 may also serve as a means for sustaining the thermo-couple element I0 and the insulators. As shown, there are a pair of uppermost insulators 25 and 26, surrounding the terminals 21 and 28. Engaging these insulators, there is a composition base 29 carrying metal connectors 30 and 3|, to which lead wires 32 and 33 are secured, which lead to the pyrometer 34. With the arrangement described, it will be apparent that only a short length of the relatively expensive chrome iron pipe I6 is needed, this being a part of the device which extends through the brickwork and is exposed to the direct action of the furnace gases. The long length of pipe I8, which serves to. position the stopper I 9 a safe distance away from 45 the heat of the furnace, is of relatively less expensive steel or iron. While the tube I6 and pipe I8 are shown as being connected by a screw threaded coupling, a non-threaded connection can also be used and in some cases the coupling 50 sleeve may be joined to the pipe and tube also by a welded body of metal, as indicated at 35 and 36.

It is also within the scope of my invention to omit the coupling I1 and extension pipe I8 and 65 to merely lengthen the tube I6 suiciently to position the stopper I9 far enough away'from the intense heat to prevent its destruction.

The'thermo-couple protective device described can be easily and quickly manufactured at a relatively low cost from stock materials and it' effects important economies in various industrial establishments by prolonging the lifefof the thermo-couples. l

While I have described quite precisely the details' of construction of the embodiment of the invention herein illustrated it is to be understood that rvarious modiiications and substitutions may be made by those skilled in the art without departure from the invention as defined in the appended claims.

What I claim is:

1. In combination,r a thermo-couple junction housed in a tube closed at one end and open at the other, said tube being of chrome iron char-L acterized by a high resistance to the destructive action of furnace gases, the closed end being adapted to extend into a furnace, an extension pipe, a screw coupling uniting the open end of the tube to said pipe, a stopper of resilient material subject to deterioration by heat and furnace gases compressively assembled in the end of the pipe remote from the coupling, a iiber disk engaging the top of said stopper and a cap screwed on said remote end of the pipe and coacting with the disk to force it into compressive 4pipe to hermetically seal the assemblage and thus prevent the destructive oxidation of said thermocouple element, said junction having leads extending through both the stopper and the disk.

2. In combination, a thermo-couple junction enclosed in a tube closed at one end and open at the other, said tube being of metal characterized by high resistance to the destructive action of furnace gases, the closed end thereof being adapted to extend into a furnace, an extension pipe, a coupling uniting the open end of the tube to said pipe, a stopper of resilient material subject to deterioration4 by heat and furnace gases compressively assembled in the end of the pipe remote from said coupling, a disk of insulating material engaging the top of said stopper, a cap screwed on said remote end of the pipe coacting with the disk to force it into compressive relation with the stopper so as to cause a portion thereof to overlap said end of the pipe to her' metically seal the assemblage and thus prevent the, destructive oxidation of said thermo-couple element, said junction having leads extending through both the stopper and the disc.

JOHN E. BUELL. 

